The present invention relates to a method of controlling and/or limiting diaphragm excursion or displacement of loudspeakers and a corresponding loudspeaker excursion controller. Methodologies, devices and systems for controlling diaphragm excursion of electrodynamic loudspeakers are highly useful for numerous purposes for example in connection with diaphragm excursion limitation. A sealed box direct radiator loudspeaker produces a sound pressure level which is proportional to an acceleration of the diaphragm or membrane such that the diaphragm excursion is the 2nd order integral of the sound pressure, e.g. representing a recorded audio signal like speech and music. Consequently, reproduction of low frequency sound pressure requires large diaphragm excursions. The resulting excursion requirement of the diaphragm can exceed the safe operating range of the loudspeaker under numerous circumstances—for example when the loudspeaker is driven by a powerful amplifier and operating at a high playback volume. In the latter situation, the power amplifier may drive the diaphragm and voice coil assembly beyond its maximum excursion limit leading to various kinds of irreversible mechanical damage.
In this case, it is desirable to reduce a level or power of the low-frequency components of the incoming audio signal before application to the loudspeaker while preserving a level or power of the incoming audio signal at higher frequencies in such a way that the maximum excursion limit of the loudspeaker is not exceeded. In connection with the control of the diaphragm excursion it is often of significant importance to maintain the perceptual quality of the reproduced sound of the loudspeaker, i.e. minimizing the audible impact of any dynamic adjustment of the audio reproduction signal path connected to the loudspeaker.
The proper control and limitation of diaphragm excursion are of significant importance in numerous sound reproduction applications such as high power loudspeakers for public address systems, automotive speakers and home Hi-Fi applications as well as miniature loudspeakers for portable communication devices such as smartphones, laptop computers etc.